Tumor reactive T-cells have been reported to mediate therapeutic responses against human cancers (Rosenberg et al., 1988). In certain instances, in human immunotherapy trials with tumor infiltrating lymphocytes (TIL) or tumor vaccines, these responses correlated either with in vitro cytotoxicity levels against autologous tumors (Aebersold et al., 1991) or with expression of certain HLA-A,B,C gene products (Marincola et al., 1992). Recent studies (Ioannides et al., 1992) have proposed that in addition to virally encoded and mutated oncogenes, overexpressed self-proteins may elicit some degree of tumor-reactive cytotoxic T-lymphocytes (CTLs) in patients with various malignancies (Ioannides et al., 1992; Ioannides et al., 1993; Brichard et al., 1993; Jerome et al., 1991). Autologous tumor reactive CTLs can be generated from lymphocytes infiltrating ovarian malignant ascites (Ioannides et al., 1991), and overexpressed proteins, such as HER-2, may be targets for CTL recognition (Ioannides et al., 1992).
T-cells play an important role in tumor regression in most murine tumor models. Tumor infiltrating lymphocytes (TIL) that recognize unique cancer antigens can be isolated from many murine tumors. The adoptive transfer of these TIL in addition to interleukin-2 can mediate the regression of established lung and liver metastases (Rosenberg et al., 1986). In addition, the secretion of IFN-γ by injected TIL significantly correlates with in vivo regression of murine tumors suggesting activation of T-cells by the tumor antigens (Barth et al., 1991). The known ability of TIL to mediate the regression of metastatic cancer in 35 to 40% of melanoma patients when adoptively transferred into patients with metastatic melanoma attests to the clinical importance of the antigens recognized (Rosenberg et al., 1988; Rosenberg, 1992).
Strong evidence that an immune response to cancer exists in humans is provided by the existence of tumor reactive lymphocytes within melanoma deposits. These lymphocytes, when isolated, are capable of recognizing specific tumor antigens on autologous and allogeneic melanomas in an MHC restricted fashion. (Itoh et al., 1986; Muul et al., 1987; Topalian et al., 1989; Darrow et al., 1989; Hom et al., 1991; Kawakami et al., 1992; Hom et al., 1993; O'Neil et al., 1993). TIL from patients with metastatic melanoma recognize shared antigens including melanocyte-melanoma lineage specific tissue antigens in vitro (Kawakami et al., 1993; Anichini et al. 1993). Anti-melanoma T-cells appear to be enriched in TIL, probably as a consequence of clonal expansion and accumulation at the tumor site in vivo (Sensi et al., 1993). The transduction of T-cells with a variety of genes, such as cytokines, has been demonstrated. T-cells have been shown to express foreign gene products. (Blaese, 1993; Hwu et al., 1993; Culver et al., 1991) The fact that individuals mount cellular and humoral responses against tumor associated antigens suggests that identification and characterization of additional tumor antigens is important for immunotherapy of patients with cancer.
T-cell receptors on CD8+ T-cells recognize a complex consisting of an antigenic peptide (9-10 amino acids for HLA-A2), β2 microglobulin and class I major histocompatibility complex (MHC) heavy chain (HLA-A, B, C, in humans). Peptides generated by digestion of endogenously synthesized proteins are transported into the endoplastic reticulum, bound to class I MHC heavy chain and β2 microglobulin, and finally expressed in the cell surface in the groove of the class I MHC molecule.
Information on epitopes of self-proteins recognized in the context of MHC Class I molecules remain limited, despite a few attempts to identify epitopes capable of in vitro priming and Ag-specific expansion of human CTLs. For example, peptide epitopes have been proposed which are likely candidates for binding on particular MHC Class I Ag (Falk et al., 1991), and some studies have attempted to define peptide epitopes which bind MHC Class I antigens.
Synthetic peptides have been shown to be a useful tool for T-cell epitope mapping. However in vivo and in vitro priming of specific CTLs has encountered difficulties (Alexander et al., 1991; Schild et al., 1991; Carbone et al., 1988). It is generally considered that in vitro CTL priming cannot necessarily be achieved with peptide alone, and in fact, a high antigen density is thought to be required for peptide priming (Alexander et al., 1991). Even in the limited instances when specific priming was achieved, APC or stimulators were also required at high densities (Alexander et al., 1991).
Short synthetic peptides have been used either as target antigens for epitope mapping or for induction of in vitro primary and secondary CTL responses to viral and parasitic Ags (Bednarek et al., 1991; Gammon et al., 1992; Schmidt et al., 1992; Kos and Müllbacher, 1992; Hill et al., 1992). Unfortunately, these studies failed to show the ability of proto-oncogene peptide analogs to stimulate in vitro human CTLs to lyse tumors endogenously expressing these antigens.
Identification of tumor antigens (Ag) and of specific epitopes on these Ag recognized by cytotoxic T-lymphocytes enables the development of tumor vaccines (for review of tumor antigens, see Rosenberg (2000), incorporated by reference herein). Tumor Ag are weak or partial agonists for activation of low-avidity (low-affinity) CTL. Attempts to activate CTL by increasing the affinity of peptide for MHC (by modifications in the anchor residues) has produced mixed successes even with powerful APC (dendritic cells, DC) and added B7 costimulation. Some of the resulting cross-reactive CTL recognized tumors with lower affinity than CTL induced by wild type Ag.
The limited ability of anchor-fixed immunogens to induce and expand high-affinity CTL raises the need for alternative approaches for CTL induction. One approach to this question is to design immunogens which activate “high-affinity” CTL from the existent pool of responders. In human tumor immunology, this approach has been successful in some instances. However, high-affinity CTL are expected to be more sensitive to silencing by elimination (e.g. apoptosis) or by anergy (unresponsiveness or diminished reactivity to a specific antigen).
These processes occur as a consequence of recurrent stimulations with Ag (tumor Ag) and are amplified by a number of cytokines. The general mechanism of activation induced cell death (AICD) is that repeated stimulations with an Ag in the presence of cytokines such as IL-2 activates cell death pathways. This is because stimulation with Ag and IL-2 transduces a signal which is too strong to induce proliferation and instead leads to premature senescence. An alternative death pathway, passive cell death (PCD) occurs when cytokines involved in survival (IL-2, IL-4, IL-7, etc.) are withdrawn. Since tumor Ag are self-Ag, the corresponding responding cells should be even more sensitive to deletion than CTL responding to foreign Ag, because the body's defense mechanisms are programmed to avoid autoimmunity. There is little known as to how the survival of responders to tumor Ag can be induced, and how they can be protected from AICD or PCD.
Preclinical and clinical trials are underway for the utilization of tumor-specific peptide epitopes for melanoma (Rivoltini et al., 1999; Parkhurst et al., 1998; Kawakami et al., 1998; Lustgarten et al., 1997; Zeng et al., 1997; Reynolds et al., 1998; Nestle et al., 1998; Chakraborty et al., 1998; Rosenberg et al., 1998); breast cancer, such as with MUC1 (Gendler et al., 1998; Xing et al., 1989; Xing et al., 1990; Jerome et al., 1993; Apostolopoulos et al., 1994; Ding et al., 1993; Zhang et al., 1996; Acres et al., 1993; Henderson et al., 1998; Henderson et al., 1996; Samuel et al., 1998; Gong et al., 1997; Apostolopoulos et al., 1995; Pietersz et al., 1998; Lofthouse et al., 1997; Rowse et al., 1998; Gong et al., 1998; Acres et al., 1999; Apostolopoulos et al., 1998; Lees et al., 1999; Xing et al., 1995; Goydos et al., 1996; Reddish et al., 1998; Karanikas et al., 1997), p53 (DeLeo, 1998; McCarty et al., 1998; Hurpin et al., 1998; Gabrilovich et al., 1996), and Her-2/neu (Disis and Cheever, 1998; Ioannides et al., 1993; Fisk et al., 1995; Peoples et al., 1995; Kawashima et al., 1999; Disi et al., 1996); and colon cancer (Kantor et al., 1992; Kantor et al., 1992; Tsang et al., 1995; Hodge et al., 1997; Conry et al., 1998; Kass et al., 1999; Zaremba et al., 1997; Nukaya et al., 1999).
Recently, peptides of folate binding protein (FBP) were recognized by tumor-associated lymphocytes (Peoples et al., 1998; Peoples et al., 1999; Kim et al., 1999). FBP is a membrane-associated glycoprotein originally found as a mAb-defined Ag in placenta and trophoblastic cells but rarely in other normal tissues (Retrig et al., 1985; Elwood, 1989; Weitman et al., 1992; Garin-Chesa et al., 1993). Of interest, this protein has been found in greater than 90% of ovarian and endometrial carcinomas; in 20-50% of breast, colorectal, lung, and renal cell carcinomas; and in multiple other tumor types. When present in cancerous tissue, the level of expression is usually greater than 20-fold normal tissue expression and has been reported to be as high as 80-90-fold in ovarian carcinomas (Li et al., 1996).
U.S. Pat. No. 5,846,538 is directed to immune reactivity to peptides of HER-2/neu protein for treatment of malignancies.
Folate binding protein provides an ideal target for and satisfies a long-felt need in the art for compositions and methods of utilizing the compositions directed to tumor immunity.